Viruses have many potential therapeutic uses, for example in gene therapy, whereby the viral genome is used as a vector for foreign genes, as well as in vaccination and cancer therapy, for example by exploiting the phenomenon of viral oncolysis, which exploits cell destruction following selective virus replication in certain tumors.
However, clinical use of viruses presents certain problems. For example, many human subjects are pre-immune to common viruses such as adenoviruses, and thus have circulating antibodies. In cases in which the circulating antibodies are neutralizing in nature, the administered viral particles may have reduced or no infectivity. Repeated administration may exacerbate this problem, since most viruses are highly immunogenic. Immune responses may also contribute to the toxicity of viral administration, and in cases in which cellular immunity is involved, some profound tissue damage may result.
In addition to problems related to the immune system, virus particles are also potentially vulnerable to other clearance mechanisms. Particulates tend to be filtered by the liver and spleen via a mechanism involving phagocytic/endocytic uptake by macrophages. Viral aggregates may be cleared by such mechanisms. In addition, activation of the complement system by viruses may be a factor involved in the inactivation of some viral vectors. Proteolysis and, where relevant, lipolysis, may also potentially damage viral particles.
Viral particles also often have highly specific tissue distribution. This is not always desirable in the therapeutic applications envisaged for the virus. For example, it is desirable in some settings to circumvent the natural viral tissue distribution, possibly simultaneously xe2x80x98targetingxe2x80x99 the virus to a new site such as a tumor. With appropriate modification of viral vectors, both active and passive targeting strategies should be feasible with such vectors. However, abrogation of tissue specific localization systems may make viral particles more susceptible to non-specific uptake mechanisms. One form of passive targeting particularly relevant to viral vectors for use in gene therapy for cancer or in viral oncolysis is the so-called enhanced permeability and retention effect, which exploits leaky vasculature and poor lymphatic drainage in tumors, which can achieve enhanced localization of particulates.
Virus particles also have veterinary and agricultural uses which share some of the above problems.
Polymer modification has been shown, in the context of polymer-protein and polymer-liposome constructs, to have the potential to solve many problems. For example, polymer cover has been demonstrated to reduce antigenicity and immunogenicity. In addition, light polymer cover can turn an antigen into a tolerogen. Polymer cover can also ameliorate reticuloendothelial system (RES) uptake of particulates. Further, polymer can serve as a linker to couple targeting devices to the surface of other molecules or macromolecular structures to target them to specific sites.
However, living viruses are very different in their characteristics to proteins and liposomes. The surface structures involved in infectivity might well be compromised by polymer modification. Virtually all clinical applications of viruses require infectivity to be maintained.
I has been surprisingly found in accordance with the present invention that viral particles can be polymer modified and yet retain infectivity. It has also been discovered that polymer modification of viruses results in the acquisition of beneficial properties such as improved capacity to infect in the presence of neutralizing antibodies.
The present invention provides viruses modified by polymers. In a preferred embodiment the polymer is polyethylene glycol (PEG). In one embodiment, the polymer is directly covalently attached to the virus. In another embodiment, the polymer is indirectly covalently attached to the virus via an intermediate coupling moiety. In yet another embodiment, the polymer is indirectly noncovalently attached to the virus via a ligand. In a preferred embodiment, the ligand has specificity for a viral surface component. For example, the ligand may be an antibody.
The present invention further provides a method of making viruses modified by polymers, whereby the modified viruses retain infectivity.
Another embodiment of the present invention provides a method for introducing a transgene into a target cell comprising contacting the target cell with a polymer-modified virus, wherein the virus comprises the transgene.
The present invention further provides a method of delivering a virus to a tumor, comprising administering a polymer-modified virus of the invention to a subject in need of such treatment under conditions whereby the polymer-modified virus localizes to a tumor.
In another embodiment, the present invention provides a composition comprising a virus modified by a polymer and a carrier.